Photolithography systems are known in the art that direct light beams onto a photosensitive surface covered by a mask, etching a desired pattern on the substrate corresponding to the void areas of the mask. In mask-based photolithography systems, the patterns generated are defined by physical masks placed in the path of light used for photo-activation. While effective, the use of physical masks in photolithography has numerous drawbacks, including the cost of fabricating masks, the time required to produce the sets of masks needed to fabricate semiconductors, the diffraction effects resulting from light from a light source being diffracted from opaque portions of the mask, registration errors during mask alignment for multilevel patterns, color centers formed in the mask substrate, defects in the mask, the necessity for periodic cleaning and the deterioration of the mask as a consequence of continuous cleaning.
Maskless photolithography systems are also known in the art as described in Singh-Gasson, Sangeet et al., Nature Biotechnology 17, 974-78, 1999. The system described in this article uses an off-axis light source coupled with a digital micromirror array to fabricate DNA chips containing probes for genes or other solid phase combinatorial chemistry to be performed in high-density microarrays.
A number of patents also exist which relate to maskless photolithography systems, including U.S. Pat. Nos. 5,870,176; 6,060,224; 6,177,980; and 6,251,550; all of which are incorporated herein by reference.
While the previously described maskless photolithography systems address several of the problems associated with mask based photolithography systems, such as distortion and uniformity of images, problems still arise. Notably, in environments requiring rapid prototyping and limited production quantities, the advantages of maskless systems as a result of efficiencies derived from quantities of scale are not realized. Further, while maskless photolithography systems disclosed in the art are directed to semiconductor manufacture, these prior art systems and methods notably lack reference to other applications lending themselves to maskless photolithography techniques.
Photopolymers that are polymerizable when exposed to light are known in the art. Photopolymers can be applied to a substrate or objects in a liquid or semi-liquid form and then exposed to light, such as ultraviolet light, to polymerize the polymer and create solid coatings or castings. In addition, conductive photopolymers are known that exhibit electrically conductive properties, allowing creation of electric circuits by polymerizing the polymers in circuit layout patterns. However, conventional methods of photo-polymerization use physical masks to define areas of polymerization. This mask based photopolymer process suffers from the disadvantages of mask-based photolithography methods including the requisite need for many different masks, long lead time for mask creation, inability to modify masks, and the degradation of masks used in the manufacturing process.
It is known in the art to create chemical analysis arrays for gene sequencing using conventional photolithographic methods. Arrays of closely packed variations of a specific formula, or molecule, are created on a substrate to allow testing en masse for compliance with desired design specifications. Using photolithography methods, different masks are used to selectively add new molecules to an array of previously defined samples in a series of sequential exposure steps. However, because many variations of a basic molecule need to be synthesized in an array, the number of masks required to create all the desired variations on the basic molecule may require up to 100 separate masks per array. Further, the object is not to produce thousands of arrays, but just a few arrays for a specific experiment. Thus the conventional mask based manufacturing techniques are not suited to molecular array manufacture because of the need for many different masks and the limited production quantities that prohibitively impact economic advantages of quantities of scale typically realized in large production runs that help offset the high cost of physical mask production.
Photochemical vapor deposition (PCVD) is known in the art as disclosed in “Dielectric Film Deposition in Low-Pressure Photosynthesized CVD processes and Techniques;” R. L. Abber, Handbook of Thin Film Deposition Processes and Techniques, 1988. Typically, PCVD uses photochemical reactions to transform gaseous molecules, or precursor gases, into a solid material in the form of a thin film or powder on the surface of a substrate. Typically, the process uses ultraviolet (UV) light as a radiation source to create semiconductor devices. The process can be adapted for use in creating integrated circuits, opto-electronic devices, microsensors, catalysts, micromachines, fine metal and ceramic powders, and protective coatings, such as titanium carbide. However, conventional vapor deposition techniques require a high-vacuum deposition chamber and require heating of the substrate to enhance the deposition process, thereby limiting the application of the process to vacuum resistant and high melting point substrates.
Accordingly, there is a need in the art for a method and system for maskless photolithography to create 2-D and 3-D patterns on objects in a rapid prototyping environment. Specifically, the method and system need to provide maskless photolithography system for creating microsensors and fluidic networks devices, molecular imprinted arrays, plastic circuits, and devices using reactive techniques. This system needs to combine ease of use, reconfigurability, and the ability to eliminate the need for the use of physical masks in device manufacturing systems employing photoreactive agent processes. In summary, the system needs to provide all the advantages of a maskless photolithography system at a reasonable cost, and include capabilities tailored to specific applications.